Does your truck have the "Max" recirculate button? If so, you're good to go. If not, the old 1 wire switch (which is NLA) isn't a good enough safe guard. The A/C is set up to switch to outside air when it gets too high of pressure. The later 2 wire switch and system will turn off the compressor when it sees to high of pressure, protecting your system from spikes and potential blow outs or ruptures (see post #3). I had my high pressure switch blow out of the compressor which ruined the snap ring groove in it so, junk one compressorSo the original style pressure switch is enough by itself? I think I'm not seeing why the newer one was brought up, and I don't want to damage a brand new system
R134A runs at higher pressures than the old R12 systems.